Is your feature request related to a problem? Please describe.
See discussions from other issues/PRs:
#25 (comment)
#51

Describe the solution you'd like
Would like to settle on what the UI for the legend items interactions should be. This would cover:

• How to handle the color picker (in current Kibana, it is opened in the same panel as the +/- buttons for removing/focusing a data series, but initial feedback was that this should be independent of that panel and open up just by click on the dot)
• How to handle chart internal data series visibility toggling. This is currently not a feature in Kibana, but the idea is that separate from actual removal/focus of the data for an actual series (i.e. what currently happens when you click +/- in Kibana), there should be a way to keep the data for a series but not render it within the chart. This includes:
  • How to show/hide a series within the context of other series being visible (e.g. if I have series a, b, c; I want to toggle the visibility of a while keeping b & c visible)
  • How to show/hide a series individually (which also toggles the visibility of the other series); an example of this is say I have series a, b, c, I want to toggle showing only a (making b & c not visible) and showing everything but a (making b & c visible).
• How to handle chart external data series filtering. This is currently the functionality of the +/- buttons in Kibana. The new chart library is agnostic to what actually happens on these events, but it is a way for an application to bind some custom functionality to these interactions so that when a user interacts in these ways, the data for identifying the series gets passed to the custom listeners which can define their own behaviors, e.g. a new query with the values passed to the listener as a filter.

Describe alternatives you've considered
See the links in the first section for some options discussed and current implementation.

Additional context

Kibana Cross Issues

Checklist

• this request is checked against already exist requests
• [] every related Kibana issue is listed under Kibana Cross Issues list
• [] kibana cross issue tag is associated to the issue if any kibana cross issue is present